The present invention relates to a railroad crosstie of molded and bonded lignocellulosic material internally reinforced against certain specific positive and negative bending stresses expected from train operations. Most conventional railroad crossties used in this country today are lumber beams, approximately seven inches thick by nine inches wide by eight and a half feet long, that have been cut from sections of live tree trunks selected to be free from soft or decayed spots, shakes, worm holes, and other imperfections. Before being placed into service as crossties, these beams are treated with creosote, an oily liquid preservative, to protect them against the effects of exposure to the elements.
The major disadvantages of using lumber beams for railroad crossties are the ever-increasing costs of raw lumber, the difficulty of applying creosote with sufficient penetration to prevent rapid deterioration of the beams, and the need to continually replace and dispose of those beams that are split, rotted and worn. As an example of this latter problem, it has been reported that the Santa Fe railroad alone renews approximately 1.6 million lumber crossties annually. A few of these ties are sold to farmers and ranchers along the railroad right of way, but most must be buried underground as current ecological considerations prohibit their being burned in the open or left along the right of way for extended periods of time.
Previous attempts have been made to develop a substitute for the conventional wooden crosstie, such as by manufacturing the crossties from synthetic resins as shown in Groff U.S. Pat. No. 3,289,940, or from concrete, steel or thin particle board sheets made from recycled ties or other lignocellulosic materials and laminated together. These attempts have not been successful, however, due to the higher cost of the substitute crossties, lack of sufficient strength and durability in some cases to withstand the cyclic bending loads peculiar to crossties, non-adaptability of such substitute materials to the use of conventional rail-fastening spikes and, in the case of the metal substitutes, electrical conductivity of the material employed. Since the metal rails fastened to the ties to form the railway are also often utilized as electrical conductors for the railway signal system, it is imperative that the crossties be electrically non-conductive so as not to create an electrical circuit between the rails and thereby disrupt the signal system.
Accordingly, a need still exists for a substitute for the conventional wooden crosstie capable of successfully solving the problems of high cost, frequent replacement and wasteful and polluting disposal while retaining the strength and spike-holding capabilities of conventional crossties.